Study On The Synthesis And Antimicrobial Activity Of Sorbic Acid And Benzoic Acid Amides Of Amino Acid Derivatives

Sorbic acid has a high antimicrobial activity, but more and more microorganisms havebeen resistant to inhibition by sorbic acid which has already been used for a long-term.Generally, sorbic acid is effective at acidic system, but it almost loses antimicrobial activity atneutral system or alkaline system. Therefore, new antimicrobials with broader spectrum ofactivity and lower toxicity are necessary to discover and develop.This thesis mainly studied on synthesis of sorbic acid amides of amino acid derivatives（SAAD，a1~a7） and benzoic acid amides of amino acid derivatives（BAAD，b1~b6） inorder to obtain novel antimicrobials.Alkyl amino acid hydrochlorides were sisthesized. The effect of reaction time, reactiontemperature and material ratio to the yields of them were studied by orthogonal experiment.With the optimal technological condition that the reaction time was3.5h, the reactiontemperature was60℃, the ratio of amino acid and SOCl2was1:3.2, the synthetic yields of allthe alkyl amino acid hydrochlorides were more than90%.Etheyl N-[1-oxo-2,4-hexadien-1-yl] glycinate (a1), propyl N-[1-oxo-2,4-hexadien-1-yl]glycinate (a2), isopropyl N-[1-oxo-2,4-hexadien-1-yl] glycinate (a3), methyl N-[1-oxo-2,4-hexadien-1-yl]-L-phenylalaninate (a4), ethyl N-[1-oxo-2,4-hexadien-1-yl]-L-phenylalaninate (a5), propyl N-[1-oxo-2,4-hexadien-1-yl]-L-phenylalaninate (a6), isopropyl N-[1-oxo-2,4-hexadien-1-yl]-L-phenylalaninate (a7), ethyl N-benzoyl-glycinate (b1), propylN-benzoyl-glycinate (b2), isopropyl N-benzoyl-glycinate (b3), methylN-benzoyl-L-phenylalaninate (b4), ethyl N-benzoyl-L-phenylalaninate (b5) and isopropylN-benzoyl-L-phenylalaninate (b6) were synthesized.The synthetic products were separated and purified by alkali cleaning, extraction,thin-layer chromatography and column chromatography. Besides, the representation ofpurified compounds were tested and analyzed by meltpoint dectection,1H NMR and massspectra. The results showed that the molecular structure was consistent with the theoreticalvalue.All compounds were evaluated for their in vitro antibacterial activity against bacteria,antifungal activity against yeast and mold. The result showed that SAAD had a higherantimicrobial activity, but BAAD exhibited little antimicrobial activity. Among all thecompounds, the minimum inhibitory concentration (MIC) values of compound a7were0.17 mM against Bacillus subtili,0.50mM against Staphylococcus aureus,1.66mM againstEscherichia coli,1.66mM against the mixed bacteria from rancidity milk,1.33mM againstSaccharomyces cerevisiae and3.98mM against Aspergillus niger. Its antimicrobial activitywas better than that of sorbic acid and benzoic acid. What’s more, the inhibitory rate ofcompound a7could reach more than90%after72h at any pH.Human skin was smeared a surface with test compounds (compound a2, a5, a7, sorbicacid) at concentration of5g/L. It showed that a2、a5and a7were not allergic to the skin.The in vitro cytotoxicity of compounds a2, a5, a7and sorbic acid for LO2hepatocyteswas studied. The cell viability was assessed by the MTT colorimetric assay. The results weredemonstrated that the proliferation of some cells would be inhibited by these compoundswhoes concentration were more than500μmol/L. When their concentrations were less than250μmol/L or equal to250μmol/L, the cell viability could reach more than80%. Besides, thein vitro cytotoxicity of compounds a2, a5, a7were similiar as that of sorbic acid. The cellviabilities of compounds a2, a5, a7and sorbic acid were not significant difference.